A lot of different medical devices are provided with a relatively hard outer shell and normally the shell is intended to protect or cover a functional part hidden inside the shell. A group of these medical devices are provided with a subcutaneous part where the outer shell during use somehow protects an insertion site e.g. during and/or after insertion of a subcutaneous part. “Protection” might e.g. imply that:                the user or the patient is not able to see the insertion needle and/or the insertion site before, during and/or after insertion;        the outer shell protects a subcutaneously positioned part from being moved and/or displaced by forces from the surrounding environment; and/or        the sterility of the subcutaneous part is not compromised before, during or after insertion.        
Such medical devices are e.g. known from WO 2006/062680 which document discloses an infusion set for subcutaneous delivery of an infusant. The infusion set (10) may include a base (14) removably attachable to an infusion site and a connector (12) temporarily lockable to the base (14). The connector (12) can engage the base (14) in a plurality of orientations. The connector (12) locks into the base (14) after at least partial rotation of the connector (12) about the base (14). The connector (12) may include flexible arms (16) which unlock the connector (12) from the base (14). The base (14) includes a cannula for insertion through the infusion site. The connector (12) includes tubing for passing the infusant. The infusant is subcutaneously passable from the tubing through the cannula when the connector (12) is attached to the base (14). According to this disclosure, radial locking—i.e. the features that prevents rotation of the connector relative to the base after mounting of the connector—is provided by the same parts providing the axial locking, i.e. the features that prevents the connector from being removed in a direction perpendicular to the skin surface on which it is mounted during use. According to WO 2006/062680 the radial locking means (42, 44) of the connector also provide axial locking of the connector relative to the base part as the connector is rotated into a locked position.
WO 2004/026375 discloses a catheter head with catheter drain in discrete rotational positions. The catheter head is used for introducing a fluid into an organic tissue and comprises a cannula housing (1) with a cannula (3), a connector element (2) with a fluid inlet (7), a guide and a fixing device. The guide device has several selectable discrete rotational positions for positioning the connector element relative to the cannula housing about a longitudinal axis (L) of the cannula. The connector element is positioned in a rotational position and is detachably connected to the cannula housing in the selected position by means of the fixing device.
WO 2008/065646 (Medingo Ltd) discloses an inserter device for inserting a fluid delivery device subcutaneously in order to deliver a therapeutic fluid to a patient. The inserter configuration includes automatic insertion and retraction capabilities where a trigger button (330) actuates a set of springs which fire a penetrating cartridge (150) downward into the body of the patient and retract the penetrating member after insertion. Further, the inserter includes safety mechanisms for preventing misplacement and inadvertent misfiring. According to the present application it is not necessary to provide an inserter device with complex means preventing misfiring as the spring causing insertion is not biased or loaded before insertion is intended. Actually, the user bias or loads the insertion spring just before insertion takes place.